“Science is best served when the results of all studies, whether positive or negative, are published in peer-reviewed journals,” said author David S. Liebeskind, MD, of University of California, Los Angeles Stroke Centre. “This is evidence of publication bias. Failure to publish negative results deprives doctors, patients, and future researchers of valuable data and intellectual discoveries.”

The analysis looked at all studies for treatments for acute ischemic stroke. Eighty percent of strokes are ischemic; they are caused by sudden loss of blood flow to the brain. Only studies published in English were included in the analysis.

The analysis found that three out of four unpublished studies, or 75 percent, had negative, or harmful, results, while only six percent of the 178 published studies had negative, or harmful, results.

“Our analysis showed that in addition to these four known unpublished studies, there likely are more small studies with negative results that are not being published,” Liebeskind said. “There is a conspicuous lack of small, negative studies, suggesting that publication bias has affected both corporate and non-corporate studies."

“Although the extent of publication bias detected was modest, it is concerning. Corporate profit incentives and academic concerns must be overridden by our ethical obligation to the people who participate in these studies, future patients and the scientific community. Rapid publication of negative studies may spare patients from exposure to useless or even harmful treatments, and from participation in futile studies.”